ZIRCONIA 



1193 



Imports of Zinc in the Year 1873 and three previous Years (as per Hoard of Trade 



Returns'). 



Crude, in cakes 

 Manufactures . 



Zinc Imported in 1874. 



Quantities Value 



22,216 tons 492,874 



252,607 cwts. 372,176 



British Zinc or Spelter Exported in the Year 1873 and four previous Years (as per 

 Board of Trade Returns). 



ZINCING- OP IRON. Iron may be conveniently coated, in the humid way, by 

 a solution of sulphate of zinc, or one of the double salts of chloride of zinc and sal- 

 ammoniac, as now used in soldering and welding. To secure success, the zinc 

 solution should be weak, and only a weak galvanic current should be used, otherwise 

 the zinc precipitated will again separate from the iron in scales. With proper pre- 

 cautions, the deposit may be made as thick as strong paper. The article must be well 

 cleansed before undergoing the operation. See GALVANISED IRON. 



ZINC PRINTING. If this art be not calculated to supersede wood engraving, 

 it can be applied with great advantage for certain purposes in the etching style, for 

 maps, plans, drawings of machines, &c. A zinc plate is covered with an etching 

 ground, the drawing etched in the usual manner with the needle, and bitten in. The 

 etching ground is now removed, the deep lines cleaned with acid, and then the whole 

 plate, in a warm state, covered with an easily fusible metal, with which, of course, 

 the lines of the drawing are filled up. When the metal thus laid on is cold and firm, 

 the whole plate is planed until the zinc appears again, and only the lines of the 

 drawing remain filled with the fusible metal, which' is easily distinguished by its 

 white colour from the gray of the zinc. The whole plate is now etched several 

 times ; the former lines of the drawing, filled with easily fusible negative metal, are 

 not affected by the acid, while the pure zinc is eaten away. In this manner a drawing 

 for printing in the copper-plate press can be converted into one in relief for use in 

 ordinary printing press. 



ZINC "WHITE. Under this name oxide of zinc is now largely used as a sub- 

 stitute for white lead. For this piirpose it is prepared by heating metallic zinc in 

 earthenware retorts, and bringing the zinc-vapour into contact with a current of air, 

 whereby it becomes oxidised. Instead of using metallic zinc, the reduction of the ore 

 and oxidation of the metal may be performed at one operation. Thus, at the New 

 Jersey Works and the Lehigh Zinc Works a mixture of ore and charcoal is treated in 

 muffle-furnaces, and the oxide obtained is blown into chambers, in which it is collected 

 in large muslin bags. In some Continental works the metallic zinc is exposed to the 

 action of superheated steam, when oxide of zinc is formed, whilst hydrogen is liberated, 

 the gas being applied in some cases to illuminating purposes. 



ZIRCON. See HYACINTH and GEMS. 



ZIRCONIA is a rare earth, extracted from the mineral zircon, which is a silicate 

 of zirconia. Zirconia itself is an oxide of zirconium. It has lately been proposed to 



